Afaan Oromo is a Cushitic language spoken by about 32 million people in Ethiopia, Kenya, Somalia and Egypt and is the 3rd largest language in Africa. The Oromo people are the largest ethnic group in Ethiopia and account for more than 40% of the population. They can be found all over Ethiopia and particularly in Wollega, Shoa, Illubabour, Jimma, Arsi, Bale, Hararghe, Wollo, Borana, and the southwestern part of Gojjam.
Until the 1970s, Afaan Oromo was written with either the Ge'ez script or the Latin alphabet Then during the early 1970s, the Oromo Liberation Front (OLF) chose the Latin alphabet as the official alphabet to write Afaan Oromo. Between 1974 and 1991 under the Mengistu regime the writing of Afaan Oromo in any script was forbidden, though limited usage of the Ge'ez script was allowed.
On 3rd November 1991 the OLF convened a meeting of over 1,000 Oromo intellectuals to decide which alphabet to use to write Afaan Ormo. After a many hours of debate, they decided unanimously to adopt the Latin alphabet.
source
wikipedia.org,
omniglot.com &
ethnologue.com